Re: Intermittent "cache lookup failed for type" buildfarm failures

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Tue, Aug 16, 2016 at 2:21 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> I grepped through the buildfarm logs and determined that there are exactly
>> zero similar failures going back as far as 2016-04-01. Now that we've had
>> four in a week, it seems certain that this indicates a bug introduced at
>> most a few days before Aug 9. A quick trawl through the git logs finds
>> no obvious candidates, though.

> Well, it would have to be something that was back-patched to 9.5,
> right? That doesn't leave too many candidates.

It's possible that the bug existed longer and was only exposed by a
seemingly unrelated change (eg, a test timing change, since it certainly
looks like it might be timing dependent). That's little help though :-(

> It would sure be nice if those cache lookup failure messages printed
> the file and line number. I wonder if we could teach psql to always
> treat the VERBOSITY as verbose when the error code is XX000.

I looked around when I saw the earlier ones of these, and had more or less
convinced myself that the errors were probably coming from one of the
lsyscache.c convenience subroutines. If that's true, we'd need a stack
trace to have much hope of identifying the cause.

regards, tom lane